Just yesterday I removed the tri bar LED rear light from my 2008 FXSTSSE2
Light had been "flickering" for long and weary , then stopped working either brake or taillight
The unit is not supposed to be user serviceable , but I "persisted" like a Scotsman ( I am a Scotsman FFsake !!)
Unbolt the unit with the 4 x 9/16 bolts under the fender , and the 2 Allen bolts from the rear
Cut the outer lens cover out of it's silicone jacket and pulled out the LED's and the circuit board
Sure enough , broken joints at the female connector to the circuit board.
Soldered with fine "silver solder" wire , rebuilt with windscreen ( sorry "windshield" haha) silicone sealant
carefully reassembled with electrical clean and lube on the wires and connectors
Working all good now , you can "tap" the light unit and no "flickering"
Only labour , your time , and a wee bit of materials.
It's a $300 light unit here in Perth Western Australia to order it from the HD dealer